Fall 2011 Climate Summary

Central Indiana

Fall 2011 Summary

As we begin the month of December, we mark the conclusion of meteorological fall and welcome meteorological winter. The fall of 2011 saw average temperatures generally near to slightly above normal. Indianapolis International Airport reached 100 degrees for the first time in September since 1954 on September 3rd. After a dry start to the fall season, much wetter conditions developed by late September, with many locations receiving normal to above normal precipitation for the rest of the fall season. The following is a summary of weather conditions experienced in Central Indiana during the months of September, October, and November 2011.

Temperatures

The fall of 2011 was tied for the 29th warmest fall ever at Indianapolis, with an average temperature of 56.8 degrees. This is 1.6 degrees above the normal fall average temperature of 55.2 degrees.

September

September began blistering hot across the Ohio Valley as a broad upper level ridge acted as the dominant weather feature. Temperatures warmed into the upper 90s across much of central Indiana for the first three days of the month, with the temperature officially reaching 100 degrees at the Indianapolis International Airport on the 3rd. This marked the first time the temperature had made it to the century mark at Indianapolis in September since September 5, 1954. The 100 degree high was a record high temperature for the date. The temperature reached or exceeded 99 degrees at Indianapolis during September 1-3, marking the first time this had happened for three consecutive days since July 1988. The only time this has occurred later in the calendar year was September 13-15, 1939.

The passage of a cold front and arrival of the remnants of Tropical Storm Lee brought an extended period of cloudy, cool and damp weather to much of the Ohio Valley beginning on the 5th and persisting through the 9th as high temperatures largely remained in the lower and middle 60s. This was a sudden and abrupt change from the hot temperatures to start the month, as average temperatures during this period were 20 to 25 degrees cooler than those experienced from the 1st through the 3rd. Temperatures warmed back to above normal levels with the departure of Lee’s remnants, with the warmest high temperatures experienced on the 12th and 13th as temperatures rose into the upper 80s and lower 90s. At Indianapolis, the high temperature of 92 degrees on September 13th marked the 42nd day in 2011 that temperatures had reached or exceeded 90 degrees. This made for the most days at or above 90 degrees in a calendar year since 1988, when the mercury reached 90 in Indianapolis on 49 days.

Temperatures turned cooler once again on the 14th with the passage of a cold front. Highs fell back into the 60s in the days to follow, with lows falling into the 40s for many for the first time in the fall on the 15th and 16th. Some locations across northeast portions of central Indiana dropped into the upper 30s on the morning of the 16th. Temperatures returned to near normal from the 17th through the 22nd, before cooler weather intervened once again beginning on the 23rd as a stubborn and very slow moving upper level low impacted the region through the 28thwith cloudy, cool and unsettled weather. Many locations across central Indiana were unable to rise out of the 50s on the 25th as rain fell for much of the day. Highs returned to the mid and upper 70s for one day on the 29th, before a cold front brought colder weather in for the 30th continuing into early October.

October

As is typical for the autumn season, the month was characterized by wide swings in temperature from nearly week to week. October started out cool for the first several days with much of the area experiencing temperatures nearly 10 degrees below normal. This was due to a persistent upper level low pressure system that lingered across the northeastern part of the country. This system finally departed the area and a strong ridge of high pressure built in, allowing for above normal temperatures through the 13th. Many areas saw highs in the low 80s for a portion of this period, which would be the last for the month. A series of low pressure systems and associated cold fronts brought central Indiana back below normal from the 17th to the 22nd.

Part of this period was marked by highs only making it in the mid to upper 40s – a shift of about 35 degrees from less than 2 weeks before. A brief warm up and return of highs in the low 70s occurred by the 26th ahead of the next cold front. The month finished out on a cool note with mostly below normal temperatures. Central Indiana experienced the coldest temperatures of the season so far on the morning of the 30th, as much of the area dipped down into the upper 20s.

November

November was characterized by a very active weather pattern with storm systems and associated frontal boundaries frequently influencing the region. There were nearly four periods of temperatures significantly warmer than normal by at least 10 degrees. These were pretty well spaced out during the month. Two of these periods were about 20 degrees above normal!

Near the 14th, much of the area experienced highs in the low 70s and lows in the mid 50s, and highs near the 26th managed to get back up to the 60s. While the majority of the month was abnormally warm, there were only a few notable brief periods of abnormally cool temperatures. The first of which occurred on the 10th and 11th, as much colder air was drawn into the area behind a strong low pressure system tracking north of the Great Lakes. Much of the area experienced highs only making it to the 40s and average temperatures approaching nearly 10 degrees below normal. The 17th was also nearly 10 degrees below normal due to the passage of a cold front.

Temperature Data for Other Sites in Central Indiana

Site

Fall 2011 Temperature

Normal Temperature

Diff. From Normal

Indianapolis Int’l Arpt

56.8

55.2

+1.6

Lafayette

55.8

54.4

+1.4

Muncie

54.0

54.4

-0.4

Terre Haute

55.6

53.9

+1.7

Bloomington

55.6

54.7

+0.9

Shelbyville

55.7

54.5

+1.2

Indianapolis – Eagle Creek

54.5

55.3

-0.8

Fall Extremes Across Central Indiana

Site

Warmest Temperature

Coldest Temperature

Indianapolis Int’l Airport

100 on 9/3

27 on 11/11 and 11/18

Lafayette

98 on 9/2

27 on 11/17, 11/18 and 11/30

Muncie

94 on 9/2 and 9/3

26 on 10/30, 11/5 and 11/30

Terre Haute

98 on 9/2 and 9/3

23 on 11/30

Bloomington

99 on 9/3

25 on 11/30

Shelbyville

98 on 9/3

26 on 11/11

Indianapolis-Eagle Creek

97 on 9/2 and 9/3

24 on 11/30

Precipitation

Overall this was the 22nd wettest fall on record at Indianapolis. The total rainfall for Indianapolis this fall was 13.06 inches. This was 3.12 inches above the normal fall rainfall total of 9.94 inches.

September

Normal to much above normal September monthly rainfall abruptly ended the summer drought in much of central and southern Indiana. Monthly rainfall ranged from slightly over 2 inches in extreme west central Indiana to more than 9 inches in portions of southwest Indiana near the Ohio River. Much of the state received 3 to 6 inches of rainfall during September. At the Indianapolis airport 5.37 inches of rain fell during the month...the most for September since the record wet September of 2003.

Almost all of the rainfall during the month fell after the 10th. A large share of the rainfall in central and southern Indiana occurred from the 19th through the 25th. A storm system moving through the region on the 19th produced much needed rainfall across most of central Indiana. Some of the heaviest rainfall fell across northern portions of the Indianapolis metro area, with many locations receiving 2 to 3.5 inches. At the Indianapolis International Airport, this was the highest daily rainfall since June 20.

A slow moving low pressure system moving across the Ohio Valley on the 24th and 25th produced a widespread 1 to 3 inches of rain across much of central Indiana. The heaviest rain fell during the afternoon and evening of the 25th from near Vincennes northeast through Bloomington and Indianapolis, where many locations received in excess of 2 inches of rainfall. The 2.17 inches of rain on the 25th at Indianapolis was a record rainfall total for the date. The only area remaining quite dry was a small portion of west central Indiana composing of Vermillion and Warren Counties between the Wabash River and the Indiana-Illinois state line.

October

October monthly rainfall varied widely across the state. Much of central and southern Indiana received near normal monthly rainfall for October of 2 to 4 inches. The least amount of rain during October fell along and west of U.S. Highway 41 in far western Indiana north of Terre Haute. The most rain occurred in portions of Porter and LaPorte counties in far northern Indiana.

All of October’s rain fell after the 11th. A November-like storm from late on the 17th through the 20th provided much of the rainfall for the state during October. Widespread rains of 1 to 4 inches fell during this time. Rainfall of 1 to 2 inches fell in portions of southwest Indiana on the 12th and 13th, northwest Indiana on the 13th and southern Indiana on the 26th and 27th. Rainfall during October and the transition to cooler weather eliminated drought conditions in all of the state by the 20th. This was a complete reversal from a year ago when drought conditions prevailed in all of Indiana.

November

November monthly precipitation was above normal for all of Indiana except the northwestern portion. Melted precipitation ranged 2 inches to nearly 10 inches in Indiana. Much of central and southern Indiana received monthly amounts of 5 to 8 inches. The least amount of rain during November fell in northwest Indiana near Lake Michigan and the most in southwest and south central Indiana. A large portion of November’s precipitation fell during the last week of the month. Melted precipitation totals of 2 to nearly 5 inches caused widespread lowland flooding. This was the first river flooding since June.

Many locations in central Indiana saw their first snowflakes of the season during the afternoon and evening of the 10th as scattered snow showers mixed with ice pellets moved across central Indiana on the back side of a departing storm system. Some locations across central Indiana received a brief dusting of snowfall, but up to 3 inches fell in portions of northeast Indiana. A much more extensive snowfall impacted the region on the 29th as cold air was pulled south into central Indiana as a strong upper low tracked through the Ohio Valley. Locally heavy snowfall developed during the afternoon and evening across northern portions of central Indiana with many locations from Lafayette east through Kokomo and Muncie receiving 3 to 5 inches of heavy wet snow. Snowfall amounts dropped off drastically further to the south where surface temperatures remained just a bit warmer. Many areas from Interstate 70 south received around an inch with locally higher amounts of 2 to 3 inches east of Indianapolis across Henry and Shelby Counties. Once again the heaviest snow across the state was in northeast Indiana where totals approached 10 inches.

Rainfall Data for Other Sites in Central Indiana

Site

Fall 2011 Rainfall

Normal Rainfall

Diff. From Normal

Indianapolis Int’l Arpt.

13.06

9.94

+3.12

Lafayette

11.87

8.52

+3.35

Muncie

14.15

10.83

+3.32

Terre Haute

13.06

9.33

+3.73

Bloomington*

12.24

10.82

+1.42

Shelbyville

15.04

10.01

+5.03

Indianapolis – Eagle Creek

13.45

9.06

+4.39

* Total at Bloomington is likely too low from November and estimates suggest the fall total above should be between 2 and 3 inches higher.

Major Weather Events

Scattered strong to severe thunderstorms occurred ahead of a cold front during the late afternoon and evening of September 3rd. The storms primarily produced damaging winds from the Indianapolis metro area northeast to Anderson and Muncie. An EF1 tornado occurred in Jennings County early on the morning of September 26th as low pressure moved through the region and triggered a few severe thunderstorms across southeast and east central Indiana.

The only other severe weather event of the fall took place on the afternoon and evening of November 14th as low pressure tracked along a cold front moving through the Ohio Valley triggering scattered severe thunderstorms. There was a funnel cloud sighted near the Lafayette Mall from an intense thunderstorm. Additionally, golf ball sized hail was reported in Bicknell in Knox County and in Frankfort in Clinton County. Wind gusts up to 60 to 65 mph were recorded near Lafayette and Terre Haute with numerous trees downed. A semi trailer and large propane tank were overturned along with some minor damage to structures near Danville in Hendricks County.

For information on severe weather in other areas throughout the fall, visit the Storm Prediction Center “Severe Weather Event Summaries” website at http://www.spc.noaa.gov/climo/online/.

Winter 2011-2012 Outlook for Central Indiana

The official outlook for the 2011-12 winter season (December-February) from the Climate Prediction Center, indicates a better chance of near to slightly above normal temperatures across central Indiana. At Indianapolis, the average temperature for the winter season is 30.5 degrees. A greater chance of above normal precipitation exists across central Indiana throughout the upcoming winter. At Indianapolis, the average precipitation for the winter season is 8.15” with 22.0” of snowfall.